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Rh Air France v. Saks, 470 U. S. 392, 399 (1985). All with an eye to ensuring both sides receive the “benefit of their bargain.” Mobil Oil Exploration & Producing Southeast, Inc. v. United States, 530 U. S. 604, 621 (2000).

That exercise entails the application of familiar principles of contract interpretation. Those principles include an implied covenant of “the utmost good faith” and fair dealing between the parties. Sullivan v. Kidd, 254 U. S. 433, 439 (1921). They include the doctrine of contra proferentem—the principle that any uncertainty in a contract should be construed against the drafting party. See Lamps Plus, Inc. v. Varela, 587 U. S. ___, ___–___ (2019) (slip op., at 9–10); see also 1 Oppenheim’s International Law 1279 (R. Jennings & A. Watts eds., 9th ed. 1992). And they include the doctrine of unilateral mistake—the notion that, if two parties understand a key provision differently, the controlling meaning is the one held by the party that could not have anticipated the different meaning attached by the other. See Restatement (Second) of Contracts §201(2) (1979).

Still other doctrines impose a “higher degree of scrutiny” on contracts made between parties sharing a fiduciary relationship, given the risk the fiduciary will (intentionally or otherwise) “misuse” its position of trust. 28 R. Lord, Williston on Contracts §71:53, p. 617 (4th ed. 2020). When it comes to the United States, such fiduciary duties must, of course, come from positive law, “not the atmosphere.” Haaland v. Brackeen, 599 U. S. ___, ___–___ (2023) (slip op., at 11–12). But the United States has, through “acts of Congress” and other affirmative conduct, voluntarily assumed certain specific fiduciary duties to the Tribes. Seminole Nation v. United States, 316 U. S. 286, 287, 297 (1942). That raises the specter of undue influence—especially since, in many negotiations with the Tribes, the United States alone had “representatives skilled in diplomacy” who were “masters of [its] written language,” who fully “underst[ood] the … technical estates known to [its] law,” and who were